VLBA Imaging at 7 mm and Linear Polarimetric Observations at 6 cm and 3 mm of Sagittarius A*

VLA and VLBA observations of compact radio cores in LINER galaxies

Bower G.C.1, Falcke H.1, Backer D.2, Wright M.C.H2

1Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany (hfalcke@mpifr-bonn.mpg.de)
2Radio Astronomy Laboratory, UC Berkeley, Berkeley, CA

in: "The Central Parsecs of the Galaxy", eds. H. Falcke, A. Cotera, W. Duschl, F. Melia, M. Rieke, ASP Conf. Series , Vol. 186, 80


We summarize the results of 7 mm VLBA imaging of Sgr A* and discuss some of the difficulties of accurately constraining the size of Sgr A* with VLBI observations. Our imaging results are fully consistent with the hypothesis that the VLBA image of Sgr A* is a resolved elliptical Gaussian caused by the scattering of an intervening thermal plasma. We show that determination of the minor axis size at 7 mm with the VLBA is very unreliable. We also present new polarimetric observations from the VLA and from the BIMA array of Sgr A*. At 4.8 GHz, we find an upper limit to the polarization of 0.1%. At 86 GHz, we report a marginal detection of 1 +/- 1% linear polarization. We discuss the effects of interstellar propagation on the linear polarization and consider the significance of very low intrinsic linear polarization in Sgr A*.

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Questions: Heino Falcke, hfalcke@mpifr-bonn.mpg.de